This has been discussed numerous times around here...Do a little searching and I think you will find your answer...MY opinion however and I think the general consensus agrees, is that the .40 cal is the best LE round.

Given only the option between the 9mm and .40 cal.............. I will take the larger .40 cal any day. Round capacity is nice, but I'll take knockdown power over round capacity if given this choice. The .40 cal S&W was created specifically to be an alternative, having near knockdown ability of the .45 cal with the round capacity of the 9mm. Over the years since it has been introduced, it has proven to be much more effective than the smaller 9mm.

There is not a significant difference between the 9mm and 40. It will come down to the specific ammo selected. With the technology in ammuntion today there are some types of 9mm rounds that will perform better than some 40 rounds. With that I will usually choose the 40 over the 9mm.

You have the rest of your life to solve the problem, how long your life lasts depends on how well you do it. -Clint Smith

One must remember that when the .40cal S&W round was developed (and its 10mm cousin) the FBI was looking for a duty pistol that provided the "knockdown power" of the .45cal with the round capacity of the 9mm. It was at the same time when the CHP (California Highway Patrol) was also looking to make changes with its standard issued duty weapon. At that time, the FBI selected the 10mm. The CHP selected the .40cal S&W, citing the fact that it had similar "knockdown qualities" of the .45cal while maintaining the round capacity and controllability of the 9mm.

As a direct result of the North Hollywood Bank of America robbery and subsequent shootout that followed, the LAPD conducted a review of its standard issue equipment which included the 9mm Beretta 92fs and the Ithaca model 37 12ga pump / Remington 870 12ga pump shotguns. Comments that came directly from the officers involved as they engaged two suspects heavily armed with AK47 fully auto-matic assault rifles and completely covered in Kevlar included that nothing the LAPD line officer had was able to provide the "knockdown power" to stop them. They watched as shot after shot of 9mm and .00 buck went into the 10 ring and bounced off of the suspects barely causing them to flinch. All commented that at a minimum, a .45cal pistol round would have been more effective as would rifled slugs in the shotgun. Neither of those were options were available and officers in the LAPD were prohibited by policy to use them. Granted, the LAPD North Hollywood Bank of America robbery was unique, when considering the method(s) and the equipment of the suspects and that not everyone we might engage will be wearing Kevlar from head to toe. I also know that the officer's acquisition of several AR-15's from a local neighborhood gun store was what ultimately turned the tide in the officer's favor long before the arrival of SWAT officers. Still, the comments simply could not be ignored. BTW, similar comments have been made about the 9mm and its ineffectiveness as officers have engaged suspects high on PCP. When the results of the LAPD review were completed, policy was amended to allow officers who choose to qualify and carry pistols in .40cal S&W and .45cal to do so. Policy also was changed to include rifled slugs as part of the issued shotgun ammunition. The LAPD has also introduced AR-15's into many of the marked patrol units making them more readily available.

In the end, whether it is mythical or not, there is much to be said about "Knockdown Power" or officers would not be choosing the .40cal S&W and the .45cal over the 9mm if they had the choice.

I carry a service pistol chambered for the .45ACP round myself. The Army switched to the .45ACP round as a result of their Moros rebellion in the Phillippines, they wanted a round that could do more damage than the previous .38 I believe. It set the standard for the combat load for 70+ years until the switch to the 9mm round, which was the most popular round of the 80s and a comformity round with NATO.

I believe the standard was set with the .45ACP and thats why I choose it, it is a round designed for one thing...stopping a trained, in shape, and motivated soldier dead in his tracks. Should be good enough to carry on the streets of Harris County.

Now having said that, I trained with and have used the 9mm loaded M9 my entire Army career, I know first hand what that round and that pistol can do to a well motivated jihadist more intent on killing me than keeping himself alive. And at the same time, the pistol I trained on in the police academy was the Glock 22, a pistol chambered for the .40S&W round. Its all I shot for 5 months.

I would have no problem carrying a pistol chambered for any of the 3...in the end, it really is about shot placement AND what the shooter is most comfortable shooting...and that goes beyond the round itself, that goes for the individual pistol frame and model.

I would have no problem carrying a pistol chambered for any of the 3...in the end, it really is about shot placement AND what the shooter is most comfortable shooting...and that goes beyond the round itself, that goes for the individual pistol frame and model.

There is not a significant difference between the 9mm and 40. It will come down to the specific ammo selected. With the technology in ammuntion today there are some types of 9mm rounds that will perform better than some 40 rounds. With that I will usually choose the 40 over the 9mm.

Because it doesn't exist. What people fail to realize is that energy received would have to be less than or equal to energy generated. If a projectile was powerful enough to knock someone down, it would also knock down the person firing the round.

Because it doesn't exist. What people fail to realize is that energy received would have to be less than or equal to energy generated. If a projectile was powerful enough to knock someone down, it would also knock down the person firing the round.

I think you mean "kills at both ends" a reference I heard from a person who accidently pulled both triggers simultaneously on a double barreled 10 guage shotgun (loaded with slugs), he had the bruises to prove it.

Shot Placement, Shot Placement Shot Placement. That is what matters. Handguns will kill a person, what matters in a life or death situation is time. If you shoot the other person, you want them to drop as fast as possible. That is why center mass shots are critical, because that is where most of the vital organs are. If you shoot someone in the ear with a .45, they have a half inch hole in there ear. If you shoot them with a .22, the have a quarter inch hole in there ear. Shot placement is what stops the fight. You have to go through your progressions. Double tap to the center mass. Still going? One to the head. Still going? One to the hip. Still going? Start all over until you drop them. Any handgun is a poor manstopper. A longarm is what is needed, and even then SHOT PLACEMENT!